1. Field of the Invention
The invention disclosed herein relates generally to a compact packaging configuration with narrow package width. More particularly, this invention relates to a novel and improved device layout and packaging configuration for combining a metal oxide semiconductor field effect transistor (MOSFET) and a Schottky diode into a narrow and compact TSOP (thin small outline package).
2. Description of the Prior Art
Referring to FIG. 1 for a DC-to-DC power converter that is becoming increasingly more important because such devices are now being implemented in more and more portable power electronic devices. Conventional packages combine a narrow MOSFET device 20′ with a Schottky diode 30′ into a dual-chip leadframe package as shown in FIG. 2. The first lead 1′ of the leadframe is for the A (anode) terminal of the Schottky diode 30′ having a T shape structure. The second lead 2′ of the leadframe is for the S (source) terminal having an I-shaped structure. The third lead 3′ of the leadframe is for the G (gate) terminal of the MOSFET 20′ having a T-shaped structure. The fourth lead 4′ of the leadframe is connected to the D (drain) terminal of the MOSFET 20′ is connected to the first metal contact 11′ of the MOSFET device 20′. The fifth lead 5′ of the leadframe is open and having an I-shape structure. The sixth lead 6′ of the leadframe is for the K (cathode) terminal of the Schottky diode and is connected to the second contact 12′ of the Schottky diode 20′.
The above-described package configuration is commonly implemented for connecting between a battery and a protective switch. However, such packaging configuration encounters several technical difficulties when implemented in a DC-DC converter with the circuit diagram shown in FIG. 1. Referring to FIG. 3 for a configuration to incorporate the DC-DC converter of FIG. 1 contained in a dual-chip TSOP package of FIG. 2 in a portable electronic device. An electric current is transmitted through an inductor L, i.e., the circuit node 40′ in FIG. 1, to the first lead 1′, i.e., the A-terminal of the Schottky diode that constituting an external electric current. Then the current is transmitted through the Schottky diode 30′ toward to the sixth lead 6′, i.e., the K-terminal of the Schottky diode 30′ constituting an internal current. Then the current is transmitted along an output direction “OUT” as shown in FIG. 3. With such packaging configuration, the external current is transmitted through a long current path as illustrated above. Since a longer current path would adversely affect efficiency of the voltage converter, the conventional packaging configuration as shown limits the voltage conversion efficiency. Additionally, a current path further complicates the circuit design thus adversely affects the design processes and also the production cost of the DC-DC converter.
Therefore, a need exists in the art of electronic device packaging to provide new and improved packaging configuration to resolve the difficulties and limitations discussed above.